The proposed research is designed to contribute substantially to our knowledge of how gene products govern embryonic cell differentiation by controlling the formation of a polar zygote. Chosen as an ideal system to investigate this problem, is the zygote of Fucus. After fertilization, the apolar zygote gives rise to two daughter cells which are different from each other in structure, function, and developmental fate. The establishment of polarity is the basis for differentiation of the first two cells of the embryo. Since this occurs synchronously in an aseptic medium, this system is amenable to cytological and biochemical experimentation. Post-fertilization synthesis of RNA and protein is required for the development of a fixed polarity and subsequent cellular differentiation. The long-range research goal is to elucidate the types, interactions and intracellular localization are of these essential gene products. The main objectives are to determine the type(s) of RNA present in the egg and synthesized in the developing zygote; to purify, characterize, and localize those "newly synthesized" glucanases which have been shown to be associated with a polar cell; to identify the biochemical intermediates and the intracellular site of fucoidan (mucopolysaccharide) sulfation; to determine the site within the rhizoid cell of "microfilaments," and their possible role in the maintenance of a stable polarity.